That may be a little overwhelming for a Pacman frog. They do need a decent amount of ground space for burrowing, but they usually feel more comfortable within smaller enclosures. This large of a tank will also be difficult to maintain correct temps and humidity levels. It can be done, but the amount of open space will make the frog feel stressed. Start out with a small enclosure especially for a baby. You cn upgrade as the frog grows.

A Pacman frog can live its entire life within a 10 gallon tank comfortably. They do become lazier as they mature and won't be quite as active so that much space is not necessary. When they are young they are extremely sensitive to the conditions of their environment and you will need to make it easy to control temps and humidity levels.