1917 can. 1262 §1 (which has no equivalent in the 1983 Novus Ordo Code) says:

[Peters's transl.:] It is desirable that, consistent with ancient discipline, women be separated from men in church.
[🇻🇦:] Optandum ut, congruenter antiquae disciplinae, mulieres in ecclesia separatae sint a viris.

A Commentary on the New [1917] Code of Canon Law vol. 6 pp. 204-5 (PDF pp. 2729-30):

§ 1. Conformable to ancient discipline, it is desirable that the women should be separated from the men in church. The very division of the ancient basilica singled out the vestibule for the penitents; the catechumens were usually admitted to the rear of the nave; the faithful occupied the side aisles, the men on the right [Epistle] side of the entrance, the women on the left [Gospel side]. Those who were held in special honor by the congregation, as widows and virgins, and those who, on account of age or social position, were entitled to peculiar regard, had their place in the forward end of the aisles or in the transept. The different orders of the clergy were in turn distinguished, the bishop had his seat in the middle of the apsidal circle, while the presbyters were seated on either side of him, but at a lower level, the deacons stood near the altar and the inferior clergy had their place with the choir in the nave.⁶⁵ In this country it will, we fear, be difficult to carry out this “desire” of the Church, on account of our custom of family pews.

No. The only place I saw that was Amish and conservative Mennonites.

It's Catholic, and older than the Amish and Mennonites. Did you notice it said, "ancient"?

repeat

In some third world novus ordo masses you can still find this. Women and children on one side, men on the other, sitting on floors sometimes. I think woman may veil as well. You’re probably more likely to see communion on the tongue and what not too.

The only place you see it in western countries these days is during traditional Confirmations where men and women are separated.