No, you can’t. Your instance will go down, but all your posts and comments will still live in read-only mode on the instances they been federated before.
In mastodon (another activity pub service) you can export your account with subscriptions, but not the posts. So, if it’ll happen, you gotta start from scratch.
Went here to write this.
Source: I’ve left Russia, where I’ve been born, after war started. Left there my whole family and all friends.