How to combine PI_Root with 24 GB filesystem?

Hello I have Ubuntu Mate installed on a 32 GB SD card on a raspberry pi 3 and currently have a 8 GB Ext4 partition labeled PI_ROOT and a 24 GB FAT partition labeled Filesystem and was wondering how to combine them so I only have one. I also have a 67 MB FAT partition labeled PI_BOOT but I think I do not need to edit that one.

Sounds like you didn’t expand the root filesystem at the initialisation.
Which version did you load?

Try reading the release notes, it used to be explained there