It lost all of my armor and level and now im just a rookie spartan with rookie armor how do I get it back
Assuming you actually did mean to post this in the Halo: The Master Chief Collection Support Forum and not the Legacy Support Forum, all of the Halo: Reach armourncan be obtained by spending Seasons Points. Season Points are earned by completing Challenges and given out for the first 100 ranks.
To get a better idea of the issue you are experiencing, can you please reply back with how you earned your armor on Reach? I’m curious if you had earned your armor on Legacy Halo Reach on Xbox 360 as if that is the case then as mentioned above progress did not carry over from Legacy titles to Halo MCC.