While there is no "official" Android 7.0 update for the Samsung Galaxy Tab A 7.0 (2016) SM-T285 , there are free community-driven Custom ROMs
Always verify checksums (MD5) of your downloads to avoid corruption.
What of the SM-T285 do you have (regional or carrier-locked)? sm t285 custom rom android 7 free
A custom recovery replaces your stock Android recovery menu, allowing you to wipe internal partitions and install custom ZIP files. Power off your SM-T285 completely.
After scouring XDA Developers and GitHub, three main free Android 7.x custom ROMs stand out for the SM-T285 (also known as or gtaxlwifi depending on variant — note: T285 is the LTE model). While there is no "official" Android 7
The Team Win Recovery Project image tailored specifically for the Spreadtrum SC9830 chipset inside your device. Download the .tar file format.
By following this guide and taking the necessary precautions, you can successfully install a custom ROM with Android 7 on your SM-T285 and enjoy a more feature-rich, secure, and customizable user experience. Power off your SM-T285 completely
: Another unofficial Nougat-based alternative found on community forums like Known Issues