Most make plates I have seen were on the drivers side near the front. But if it is several years old it may be gone or unreadable.
Your title should have a serial number even if it doesn't have a date. With that I would phone or email Jayco with a request for information.
Last would be a few photos showing the outside closed with measurements of length of the box, height and interior shots showing options and layout. Colors inside and out change from year to year and maybe someone will recognize it.
2017 SLX 195RB
2021 Jeep Grand Cherokee Summit L 5.7L V8
Andersen WDH hitch, Renogy 100 AH Lithium &
200 Watts solar panels from Renogy
Prev. '14 Jeep Grand Cherokee Overland, gas 3.6 V6