@MamePPCA1
Yes, format = erase everything.
So you should backup all your data
before formatting. And when it's done, you can replace all your data on the new partitions.
To backup you can use
BackUp (68k) or
BackItAllUp.
"Mount" means the partition will be "enabled" so you will be able to use the files on that partition.
"Boot" means you can place an AmigaOS system on that partition (C, Devs,...) and you can boot from it.