I quit playing about a month ago. I have a farm account with IM30. How do I log into that account?

You can log into any game you have bound previously to IM30. Go to the settings menu (three dots at the top of the expanded main menu) and choose the account option. Then select 'Switch account' and choose the IM30 option.

If you want to keep the game that is on the device now then make sure that you bind it to a DIFFERENT IM30 account first.