Let's start by converting all measurements to centimeters.

7m = 700cm
4dm = 40cm
4cm = 4cm

Adding these together: 700cm + 40cm + 4cm = 744cm

3m = 300cm
7m = 700cm
6cm = 6cm

Adding these together: 300cm + 700cm + 6cm = 1006cm

Now, subtracting the second measurement from the first measurement:

1006cm - 744cm = 262cm

Therefore, 7m 4dm 4cm - 3m 7m 6cm = 262cm.