at least now there is no real system for migrating to you have to make a new account and subscribe to everything again
Here is a full list, i suggest taking a local one or one that fits your interest https://join-lemmy.org/instances
sopuli or lemmy.tf seem to be good and not too big by now

here is in general a good tutorial regarding how to start and how lemmy works https://lemmy.world/post/37906