You’d want to import the server using SFTP to prevent file permission issues.
AMP has built-in SFTP, you connect by grabbing a link from the upper right of the file manager, with the username/password being your panel credentials. (using WinSCP or FileZilla)
There’s a guide you can follow here that outlines importing a server:
https://discourse.cubecoders.com/t/how-to-import-an-existing-minecraft-server-into-amp/1822
Then there’s a Forge FAQ here if you run into anything weird:
https://discourse.cubecoders.com/t/forge-frequently-asked-questions/2982/1