If there is impurity on the shoe, it is not permissible. But usually, any impurity you step on, it goes away by walking. Therefore, if you are not 100% certain of the impurity being on your shoes, it is permissible to pray in them.

I read in the description of the prophets prayer in this website that it is allowed to pray wearing shoes then how about the purity of the shoes because we walk on many impure things?