Students will learn how to represent numbers within 1000 using place-value blocks. Next, students will learn how to identify the value of a digit, for any number less than 1000. For example, the value of 4 in 342 is 40. Here's an excellent video you can show your students. They can practice this skill here. After that, students will use their understanding of place value to rearrange digits to make the smallest or largest number possible. For example, given the digits 9, 0, 4, the smallest number they can make is 49, and the largest is 904. To learn how to create the largest number, students can watch this and practice here.
Intro to place value by Khan Academy
Hundreds, tens, and ones by Khan Academy
Conclude by leading this investigation:
2.NBT.A.1: Understand that the three digits of a three-digit number represent amounts of hundreds, tens, and ones; e.g., 706 equals 7 hundreds, 0 tens, and 6 ones.