If GParted does not detect a filesystem on that partition, it is very unlikely that there is anything on it that can be mounted with standard tools.
Mounting means "making a block device available as a subtree of the Linux filesystem tree". For that you generally need support either directly in the /bin/mount command, or a filesystem support sub-command typically named /sbin/mount.xy for filesystem type xy.
There is a limited number of those:
sh@balrog:~$ ls -1 /sbin/mount.*
/sbin/mount.cifs
/sbin/mount.exfat
/sbin/mount.exfat-fuse
/sbin/mount.fuse
/sbin/mount.lowntfs-3g
/sbin/mount.ntfs
/sbin/mount.ntfs-3g
(from my Xubuntu 18.04 LTS)
And all those filesystem types are known to GParted as well, so if it was one of these, GParted would show it. It would also show if a partition was part of an LVM or encrypted (LUKS) or part of a RAID.
You can still check some more with lsblk and lsblk -f, but don't get your hopes too high. For all intents and purposes, if GParted doesn't know it, you can't mount it.
That also means that you can't resize it because for resizing you'd need tools that are even more specialized. The only thing you can do with that partition right now is to delete it.
