Force Calculations involving the velocity

Hi guys, I'm working on a little project and have come across a little problems in terms of calculating the force. I am implementing a device which takes recordings at set intervals of times and records movements (Accelereometer) in all 3 axis. This device is always constantly moving with various speeds, as were I get a little confused. Okay So this is the data I have and am recording....

Time (the time intervals are 10 milliseconds apart)

Displacement (in regards to accelerometer) (from intitial position)

Velocity (Speed in km/hr)

Can anyone help me with this? I've run a few things but I keep getting unknown variables in my equations. I know i'm missing somethign simple but I don't kno why.