I was wondering how I should pray during school camps in Australia, where there is no way to wash myself as we are in the wilderness for 4-5 days after having to pee. I knowing if pee goes on your underwear you can’t pray because you are impure, so what should I do for future references

First of all, it is very strange that you can not wash, as all you need is small amount of water.
However, if you are really unable to wash, then you can offer the prayer without cleaning the place.
However, you need to take care to keep your underwear clean.