It may be a unique part number, SKU, or serial number for a cable, electronic component, or filter (similar to how "35" or "883" might appear in catalogs) that has been paired with ".mp4" mistakenly or as part of a file naming convention.
Devices that capture analog video into digital MP4 format. 35883mp4
If you can tell me where you saw "35883mp4," I can better identify if it is a part, a file, or a code. Standard Series General Purpose 3 RCA Video Cable 10ft It may be a unique part number, SKU,