Types of Clouds:-

High Level Clouds (6 to 20 km):

Cirrus (Ci)
Cirrocumulus (Cc)
Cirrostratus (Cs)

Medium Level Clouds (2.5 to 6 km):

Altocumulus (Alt-Cu)
Altostratus (Alt-St)

Low Level Clouds (Below 7000 feet):

Stratocumulus (St-Cu)
Stratus (st)
Nimbostratus (Ni-St)

Clouds with Vertical Development (2 to 30000 feet):

Cumulus (Cu)
Cumulonimbus (Cu-Ni)

For more information visit:
http://www.superteacherworksheets.com/weather/cloud-types-article_WMWFQ.pdf