Translation:In Poland there are only three small deserts.
Right now Wikipedia actually lists as many as seven deserts in Poland, although it seems that "Wielka Pustynia Błędowska" encorporates several of them. https://pl.wikipedia.org/wiki/Kategoria:Pustynie_w_Polsce
I don't think that most Polish people know about any other than the Błędów one. If they even know about that one.
This is not entirely true, there are cases where it is appropriate to end in only, however I would say that this one is one where you generally wouldn't. You could say something like 'I want three chairs only!' which gives the sentence a whole different meaning to 'I only want three chairs!' where the former is a clear instruction and the latter is more of a desire. Ending with it tends to make the number more exclusive.