Account -> Settings -> Export to a JSON file, then in the new instance after creating your new account Import it. It will remember your community subscriptions and block lists, but if people send messages to your old account there is currently no way to forward them to the new. You could put a message in your old account (Bio area I guess?) to let people know.

@Blaze@feddit.org has some nice lists of instances to move to, if you haven’t made a decision yet. Like lemm.ee if you want access to everything on the Fediverse - including hexbear.net and lemmygrad.ml that I don’t recommend but you do you - and is the #3 Lemmy instance by size, or sh.itjust.works (#4 instance) seems quite nice. Conversely, Lemmy.cafe (UK) or quokk.au (Australia), or dubvee.org are the only ones defederated from the big three tankie instances including even lemmy.ml, if you want that. Lemmy.ca for Canada, feddit.org German + English, lemmy.dbzer0.com for anarchism, Discuss.Online for USA, and ofc there are themed ones as well.

Here is a really nice website tool to help show you info about each instance: https://lemmy.fediverse.observer/list.