How to restore .wt backup file to local MongoDB?
Community wiki answer:

*.wt are binary data files used by the WiredTiger storage engine. Individual files are not usable as a standalone backup. If you want to take a file copy backup of a MongoDB dbPath you need to include all of the files using a Supported File Copy Backup Method.

If you have a valid file backup you can use it as the dbPath for another mongod instance. Aside from copying files, there is no restore special restore process for a file copy backup.

Can you clarify what files you have in your backup?