The ornamental design for a pacifier for babies, as shown and described.
1. Pacifier for babies
1.1: Rear
1.2: Front
1.3: First plan view
1.4: Second side view
1.5: Bottom, right perspective view
1.6: Bottom, left perspective view
1.7: Third side view
1.8: Fourth side view
1.9: Front, left perspective view
The design shows the shape and ornamentation of a pacifier for babies; the broken white lines and the portion of the pacifier for babies shown inside the broken white lines in reproductions 1.2-1.9 do not form part of the claimed design.