You can export/import subscriptions, block lists, user tags and something else I'm feel like I'm forgetting

To export go-to lemm.ee/settings and scroll to bottom to "Export", import is the same way on your selected new instance.

You can't export/import posts, comments or votes on Lemmy unfortunately, however, they will live on on the Lemmy-verse network. .ee comms and their content will be cached by all the other active instances and .ee user contributions to remote comms (relative to them/you) will remain