You posted a replacement part photo of the gimbal end covers, but your gimbal roll arm beam looks snapped in half. There is way more wrong with it than a missing cover. I fix stuff like this every other day. The main frame is also bent where the cover needs to go back on so that will need to be heated up and re-bent into its original position. You will need new rubber gimbal mounts. You don't need new side covers unless you lost them.
The posts about reflashing the software only needs to be done if replacing the motherboard, camera, or any of the 3 gimbal axis motors. This can be done with the complicated Py-Serial method or go to Drone-hacks.com where it is much easier, just takes longer. And free.
If any of the 3 tabs on the pitch motor (left side that is disconnected) are broken off, which it looks like one of them is, typical really, then you need a new pitch motor. the tab can be glued back on if it is still inside the rubber mount.
If you have any error codes that say gimbal stuck, you most likely have a bad ptz signal cable. with the shape of the gimbal, I would recommend replacing it even if it works, it has been stressed pretty bad and may fail in the near future then its labor cost all over again.
If you have Care Refresh DJI will tell you how much it will cost to fix then send you a brand new drone. If DJI cant help you, mail it to me. Look up TC Drones in St Paul MN on google. I have nothing but 5 star reviews. I charge $125 labor plus parts. The gimbal mounts are $10, roll arm $20, the pitch motor is $50, the signal cable is $20, you know the cost of the missing side covers. The missing lense cover is $9. The yaw axis bracket looks broken as well, that is $60 with the yaw motor that I suspect the ribbon cables are torn. If you go to Ali Express, you can find better prices but wait times are longer, 12-21 days. if you find an Amazon seller with wait time like that, they are just getting parts from Ali Express, marking up the cost for profit and reselling. At this point I would just buy a whole gimbal assembly minus the camera for $112 on Ali Express.
From what I can see in the single photo, this is what I can tell you needs to be fixed. Im thinking there is more wrong that isn't revealed in the photo. Call me if DJI wont help you, but I can.