Where is the transmission oil tank ?

Hello, I would recommend that you stick to not driving the vehicle since the fluid is not identified. The transmission oil pan is mounted directly underneath the transmission, and there is likely no dipstick for checking the fluid level. If the fluid is red, and the power steering works fine, then it is likely from the transmission. The transmission leak will also be between centered around where the center console is. If you need further assistance, let me know, otherwise, here is a list of certified shops in your area and repair your vehicle: http://repairpal.com/bmw-within-10-miles-of-burlington-north-carolina-27215