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.