In HSK 1 grammar, under 词类 → 名词 → 方位名词, the forms include: 上、下、里、外、前、后.
上
shàng
up; on; to go to
下
xià
down; below; next
里
lǐ
inside; in
外
wài
outside; foreign
前
qián
front; before
后
hòu
after; behind
暂无。