In the first volume of the fourth grade mathematics, the unit that needs to be measured with a tape measure is "Unit 3: Length Unit". Inquiring about the fourth grade mathematics course, we can know that in the third unit, students need to learn the concept of length, the conversion of length units, and how to measure length with a tape measure. Specifically, students need to master the conversion methods of centimeters, decimeters, meters and other length units, and how to measure and compare lengths with a tape measure. Through the study of this unit, students can better understand the concept of length and the use of length units, and improve their measurement and calculation ability.