These are correct:
"The Urals separate Europe from Asia."
"Urals" is a plural noun and is the subject of the sentence, so the verb form is "separate."
"The Ural Mountains separate Europe from Asia."
"Ural" is functioning as an adjective. "Mountains" is capitalized because it is part of a name. The name is grammatically a plural noun and is the subject of the sentence, so the verb form is "separate."
"The Ural range separates Europe of Asia."
"Ural" is functioning as an adjective. "Range" is a singular noun and is the subject of the sentence, so the verb form is "separates."