Title says it all. This question inspired this meta-Q. So, are questions about removing another OS but Ubuntu on-topic?
mint is offtopic on askubuntu. But you can format the partition with mint on it with gparted. FOr the remainder: mount the partitions and you can c/p data. – Rinzwind
@Rinzwind while Mint is off-topic, I don't believe this question truly is. the OP wants to remove Mint(and maybe Windows as well) and keep Ubuntu. If a question about removing another OS and keeping Ubuntu is really off-topic, there are a lot of questions on askubutu about removing Windows and keeping Ubuntu that are off-topic as well..... – TrailRider Aug 15 '12 at 0:21
BTW, I edited the tags/title to be easier to search, but I still think that there should another dupe.
If you haven't noticed this Q doesn't need TLDR!
Relevant: Is this the right place to ask a question about installing another OS on an Ubuntu computer?