The increasing order of acidity will be 1 < 3 < 2. Acidity depends on mainly two factors :
(1) ease of proton release
(2) stability of conjugate base formed. In example
(3) the ether O exerts a I effect and is closer to COOH group than in 2 (1 effect diminishes). Also the conjugate base formed will be stabilized by the same – I effect by delocalization of charge.
