Ana - an idea is:
You could use the "member codes" area in the admin panel.
When you create a member code, for example; ana2021 - you then are presented with a registration link.
You can use this registration link to give to your 320 members to easily register an account. Their new account is automatically "linked" to your new website via the member code they used.
That's the easy part. The more difficult job is creating your website again. BUT - think about it as a fresh start for the new year.