Assuming it is their lengths that you want to measure, centimetres for your feet and millimetres for your toes.
+++
I would advise consistency - use one or the other but not both. Mixing them like that is not good practice, and you won't find such mixtures used in laboratories and workshops.
'
Strictly speaking the metre and the millimetre are the "Preferred Units" but the SI tolerates the centimetre for everyday things like clothes sizes. Please don't shoot the messenger: the metric system and its SI offspring were never designed around human proportions!
If you want to use an English unit, you should use inches. If you want to measure using the metric system, you should use centimeters or millimeters (depending on how big the toe is).
Assuming it is their lengths that you want to measure, centimetres for your feet and millimetres for your toes.
it's centimeters
cm or mm
millimetres
mm
Metres, to measure its length or width, square metres to measure its area.
None! I would measure in centimeters if I were you!
Most like a vernier caliper for accurate readings
metric unit
mm
centimetre
Kilometres
Metres, to measure its length or width, square metres to measure its area.
I would go with millimetres
None! I would measure in centimeters if I were you!
the metric system
The width of a pencil would be the metric unit of centimeters
Most like a vernier caliper for accurate readings
The metric unit of the meter would be the appropriate measure of the area of classroom. Calculating area involves multiplying the length (in meters) of the classroom's length and width. Area of the classroom would be in square (^2) meters.
Yards if you work in imperial units or metres if you work in metric units
Millimetres (or centimetres to one decimal place).