There is no legal free version of the FlyJSim 727. However, you can try the FJS 727 Classic (payware) or the free 727 Series by X-Trident (older version for XP10/11, limited systems).
The search for "FlyJSim 727 modsfire" reveals a intersection between a high-fidelity flight simulation addon and a common file-hosting platform. FlyJSim's Boeing 727 Series Professional (notably version 3) is a celebrated study-level aircraft for X-Plane, while ModsFire is a platform often used by the community to share both legitimate enhancements and, occasionally, redistributed files The Flight Simulator: FlyJSim 727 Series Professional flyjsim 727 modsfire
Download file FlyJSim - B727 Series Pro v3.rar - ModsFire.com There is no legal free version of the FlyJSim 727
If you are navigating the landscape, here are the types of high-value mods you should look for. Disclaimer: Always verify file integrity and scan for malware when using third-party hosts. FlyJSim's Boeing 727 Series Professional (notably version 3)