Standalone to membership

Welcome to the forum, @babak147! Sorry for for the trouble getting set up just now.

I have a standalone account

At the risk of sounding condescending or nit-picky, there is no such thing. I mention it because it's important we both understand words to mean the same thing, when discussing your important data. An "account" means a 1password.com account, where you've signed up for a 1Password membership. "Standalone" means that you're using 1Password on your own device only, creating and keeping data there, unless you chose to use one of our advanced, 3rd party sync methods like Dropbox or iCloud. The two are completely different ways to use 1Password, which is why "standalone account" does not exist. Can you tell me a bit more? Are you trying to use 1Password just on your local device? Or do you have a 1password.com account that you can sign into in a browser?

...app says it frozen, the only way to unfreeze it is to pay for a family plan for 6.99 a month.

If you have a frozen 1password.com account, that means the trial has expired. If it is telling you it's a $6.99 monthly charge for 1Password Families...that means at some point, you signed up for a 1Password Families account. If you don't want it, visit Preferences > Accounts and sign out of the Frozen account.