Hi I’m having problems when I add a mode some of the weapons and armor will have a red mark and you can’t see theme. Any help

Open FOMM and left click on the tab "TOOLS". In the drop down menu, if there is not a check mark to the left of "Archive Invalidation, left click on "Archive Invalidation". A box will appear with the question "Apply archive invalidation?". Choose yes. If there is a check mark to the left of "Archive Invalidation", than left click on "Archive Invalidation". A box will appear with the question "Remove archive invalidation" Choose yes and close FOMM. Open FOMM and left click on the tab "TOOLS". In the drop down menu, left click on "Archive Invalidation". A box will appear with the question "Apply archive invalidation?". Choose left than start the game.
If this did not correct the problem, you have missing meshes and you did not install the mods correctly.
If you do not have FOMM, FOSE, B.O.S.S., ArchiveInvalidation Invalidated! and FO3Edit, you should download them immediately, read the readme for each and also get the instructions for FO3Edit and use these to handle installing mods, starting the game and creating a merged patch and generally maintaining a smooth running Fallout 3 experience.

Thanks man I will try that and see.