Ext. Drive

Is There Any Way I Can Fit My Ext Drive Internally On My Pc

IN your pc?

Remove it from the enclosure.

If you want a removable, rather than external, then you need a drive caddy, rather than an external case - the 3 1/2" drive fits in a removable tray, while the tray enclosure fits in a 5 1/4" bay.

If you want to swap them, best to buy identical models - unfortunately, they never seem to offer additional trays.