Hi Eva,
To report an old account, or get help recovering it:
Click the 3 dots ( ...) in the top right side of the account's profile
Click Report/Block
Choose This is my old profile, then select an option:
If you select Recover this account, it's hacked, you'll be logged out of your
current account and taken through steps to help recover the hacked account
If you select Close this account, the profile will be reviewed and deactivated
after we're able to verify that it's your old account
Note:
You can only use the This is my old profile option if you aren't friends with the account. If you're friends with your old account, you'll need to unfriend it first.