Newbie pacman set up questions

[Samuel Little]

I'm the new guy so first off. Hi everyone!! I got very newbie style questions about a pacman set up to ask if you require a photo to help answer any of them feel free to ask.
Will a 30x30x30cm exo terra be ok from baby to adult?? I got space for a longer tank but not wider if not.
I keep milipedes and they,re plastic viv gets to 21c in winter about 24-25c in summer without a heat mat would a 6inch x 11inch habistat heat mat I have spare be enough on the side for the pacman exo terra to reach it's required temp? And where would you place the thermistat prob???