1 mm = 0.00328 feet so 30 mm = 30*0.00328 feet = 0.0984 feet
120 mm = 0.39 feet.120 mm = 0.39 feet.120 mm = 0.39 feet.120 mm = 0.39 feet.
3940 mm = about 12.9 feet.
3500 mm = 11.48 feet.
About 0.00328 feet per mm
1 mm = 0.00328 feet so 30 mm = 30*0.00328 feet = 0.0984 feet
The answer depends on the units used for 30x30. There will be different answers for 30 mm x 30 mm, 30 metres x 30 metres, and 30 miles x 30 miles! There is no justification for assuming that the measures are 30 feet x 30 feet.
120 mm = 0.39 feet.120 mm = 0.39 feet.120 mm = 0.39 feet.120 mm = 0.39 feet.
50 mm = 0.164 feet
5000 mm = 16.4 feet
970 mm = 3.18 feet
121 mm is 0.396982 feet.
1690 mm is 5.544619 feet.
12 feet is 3,657.6 mm
3940 mm = about 12.9 feet.
3500 mm = 11.48 feet.
About 0.00328 feet per mm