I've been DM for like 2-3 months and one player who's playing a Fighter (arcane archer) wants to multiclass into Ranger. Arcane Archer is not a spellcaster so assuming he will go Fighter 11/Ranger 9 how many spellslots should he get as 9th lvl Ranger. Should it be 4/3/2 or 4/2 only? I don't know too much about multiclassing yet so guys help.
That character should have spell slots of a 9th level Ranger: 4/3/2
The multiclassing rules for spellcasters is only invoked once you have more than one class which gives you the spellcasting feature. The relevant excerpt from the multiclassing rules:
Once you have the Spellcasting feature from more than one class, use the rules below. If you multiclass but have the Spellcasting feature from only one class, you follow the rules as described in that class.
--- Player's Handbook p. 164