Marcos,
PBR support for the Nexus 9300-EX series started with 7.0(3)I5(x). For a stable release that includes PBR support, I'd recommend 7.0(3)I7(5a). The I7 train is the proposed, upcoming long-lived release for the Nexus 9000 platform.
You can actually see this recommendation here:
"Customers with newer deployments and future upgrade plans are encouraged to look at Cisco NX-OS Release 7.0(3)I7(5a) and any later 7.0(3)I7(x) maintenance releases as primary candidates as they become available."
Here's the PBR Configuration Guide for 7.0(3)I7(x). I'd go over the Guidelines and Limitations as well.
Hope that helps!
- Andrea, CCIE #56739 R&S