Number and operations in base ten

2.NBT.A.3

Read and write numbers to 1000 in numerals, number names and expanded form.

Practice for this standard

Place value

Tens and ones through millions and thousandths, expanded form, and reading numbers out loud correctly.
Counting and number sense

Counting on, skip counting, number recognition and the early number sense that everything else is built on.

Official wording and the full standard: CCSS.MATH.CONTENT.2.NBT.A.3