Thanks for asking this question. My guess is the sliding glass does not work and you cannot find the motor because someone removed it and did not replace it.
If you drop the headliner, you should see the motor towards the front of the vehicle with three screws mounting it to the roof.
I am attaching the entire process below so please take a look at the instructions and get some pictures of what the roof looks like with the headliner dropped down and I am sure we can locate where it should be.
Thanks
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Sunday, May 8th, 2022 AT 6:30 PM