I am not sure why you have PAF4.gid, I have checked 4 system shere and do not have that type of file.
If you did a proper PAF 4 backup file eg name.bak then PAF 5 can restore that file for you and convert it to PAF 5.
To do this click File then Retore and at the bottom of the Backup Source window where it say PAF 5 *.zip push the dropdown tab at the end and select paf 3/4 *.bak type then select the file and click restore.
If you did not do a PAF 4 backup then it will be more complicated. Let me know