Let's start by listing the titles of all the Songs, and noting that you can read them in full here.
I'll now discuss various possible pairings among these poems, but bear in mind that there's no definitive answer to this. Arguments could be made for many different ways of pairing up, and we're never going to have a perfect bijection. It's almost an exercise in combinatorics!
Common titles
The easiest poems to pair off are those which have identical titles in both Innocence and Experience:
"Introduction" and "Introduction". Admittedly this pair don't have all that much in common besides both having the same title and coming at the start of their respective collections.
"The Chimney-Sweeper" and "The Chimney-Sweeper". Structually this pair don't have much in common either, but they're both about children who clean chimneys, almost the only mention of such among these Songs. See also my answer here which compares them in more detail.
"Holy Thursday" and "Holy Thursday". Again, not much in common except the titles: the Innocence poem is more descriptive with longer lines, the Experience poem more abstract with simpler structure.
"The Divine Image" and "A Divine Image". At first glance these don't have much in common either ... but both are about certain capitalised traits, virtues and vices respectively: the Innocence poem makes much of "Mercy, Pity, Peace, and Love", while the Experience poem bemoans "Cruelty", "Jealousy", "Terror", and "Secrecy".
"Nurse's Song" and "Nurse's Song". The parallelism between these two is perhaps the clearest of all, with even some of the lines being identical across both poems.
"A Cradle Song" and "A Cradle Song". Again, these two share some lines as well as their titles, and the essential nature of both poems is the same - watching over a sleeping child - although of course their attitude and outlook are different.
"The Little Boy Lost" and "A Little Boy Lost". Another case where the poems have little in common beyond their titles: the boy in the Innocence poem very literally gets lost from his father while walking, whereas the boy in the quite horrific Experience poem is taken by a priest to be tortured for speaking wrongly about love. (I didn't expect the Spanish Inquisition in these poems!)
Opposite/complementary titles
Some poems in Innocence and Experience can also be paired off because their titles are somehow 'opposite' to each other, as indeed are the collection titles "Innocence" and "Experience" themselves.
"The Lamb" and "The Tyger". There is certainly parallelism here beyond the titles: in both poems, the writer asks the respective animal "who made thee". The comparison is even made explicity by the line in "The Tyger" which says "Did He who made the lamb make thee?"
"Infant Joy" and "Infant Sorrow". These are two very different takes on the birth of a newborn baby. No direct parallelism in the text, but the topic is similar enough for them to be paired.
"The Divine Image" and "The Human Abstract". As above with the two Divine Image poems, both of these spend a lot of time on capitalised traits. In fact, this time "Mercy", "Pity", and "Peace" star in both poems, although of course the attitude and outlook are very different between Innocence and Experience.
"The Little Boy Found" and "The Little Girl Found". Not that boys vs girls is at all an Innocence-Experience comparison, but I noticed that both of these poems tell very similar stories, although at different lengths. In both, God appears to reunite a lost child with their parents in a "dale" or "dell". (In fact, "The Little Girl Found" seems like a very un-Experience-like poem!)
Other parallelisms
"The Echoing Green" and "The Garden of Love". I mention these two because I found a few sources which describe them as paired poems, for example this and this, but to be honest I can't see the connection myself.
"The Blossom" and "The Clod and the Pebble". I hadn't realised it until recently, but both of these poems can be interpreted comparisons between different kinds of love, symbolised by the robin/sparrow and clod/pebble respectively.
Doubtless there are more parallels which can be drawn between specific Songs of Innocence and of Experience. I've just picked out those correspondences which I found most obvious, and even here the same Song of Innocence can be paired with more than one different Song of Experience. Again, there's no definitive or unique answer to this, and nor should there be. Blake wrote his poems to be open to more than one interpretation, and he didn't compose them to correspond to each other with mathematical precision.
References
