DLC

I am quite desperate could you please help me? I have downloaded Forza Motorsports 5, 6, and 7 (I also bought almost all of the DLC for the games) in my 2014 OG Xbox One.
Now i haven’t played my Xbox for almost 2 years then when quarantine hits so i have dusted my Xbox One and turned it on to my surprise all the DLC content of FM 5 and 6 were not loaded to my garage but when i went to marketplace all the DLC were labeled as purchase… Why my DLC cars were not loaded to the garage unlike my Forza Motorsport 7 game and what should I do?

If you go to the My Games & Apps tab on your Xbox, then go to the tile for the relevant game. Press start and go to Manage game & add-ons, have a look under the ready to install tab.

Hopefully the DLC you have purchased is sat there, ready for you to install.