You will need to purchase or borrow the tool used for measuring fluid level. I hate to call it a dip stick; as such sticks measure from the top of the tube to the fluid level. The tool is a flexible shaft (much longer than the tube) that has a plastic ruler made to the end which gauges the level of the fluid above the bottom of the pan.
Unfortunately the level has to be such at a specific temperature which only can be determined by a scanner.
Bosch Master, ASE Master, L1
33 years MB technician