Recover files from disk with extundelete

Hello I need to recover files from an external drive (4TB) is not partitioned what commands can I use to do this with extundelete program I am probably typing something wrong in terminal ? Second question Is there an option to search by keywords with this program or like this ? For example, with the help of photorec recovered files had some random names (not original) so that finding the right one is hours of searching, maybe someone has experience how to efficiently search for these are photos.