Im new to crysis 2 and Im trying to get mobility enhance but it says I need to be at suit module 6, so I was wondering how you get that.

Rank up Power. I'm not entirely sure on what actually helps rank it up faster but once you reach level 6 those modules will become unlockable. Just play like you normally would then after each match you will see each suit mode will receive exp. For example, killing people in Armor mode helps rank up Armor, using stealth tactics like killing a person after you uncloak helps rank up Stealth. I'm just guessing here but I would assume ripping off mounted guns and power punching people could help rank up Power, sprint could also maybe help rank it up. But like I said, I'm just speculating. Also on a final note, each time a mode upgrades a level you will receive a module unlock that you can use on a unlockable module. Hope this helps.