Hello and welcome!
Carrying a 40 gallon about is definitely going to present a struggle for you! Is there any way a friend could perhaps drive you? A 40 gallon tank will weigh about 58-60 pounds when empty so carrying it will be tough without something like a cart to push it in. Besides it being extremely heavy, it will also be extremely awkwardly sized and thus difficult to have on you in general. If you absolutely can't get someone to drive you, I'd recommend that you get one or two others to help you carry it and hold on your laps (because I think you'd also get some disapproving looks when half your seat is being taken up by a tank). Good luck getting it home, someone on here may have some better tips
Best wishes