Answer:
1: 7.8 cm
2: .7 cm
3: 5.55 cm
For the other questions, you have to use a ruler yourself and measure using cm. :)
1 cm = 10 millimeter. To convert, just add a 0 to the end of cm to find the mm (or move the decimal one place to the right.)
For example, 2.6 cm = 26 mm / 5 cm = 50 mm. Hope this helps!