This passage lists the 31 kings that Joshua defeated. After that listing, the story turns to Joshua, an older leader, surveying the remaining land to be taken: the land of the Philistines, Geshurites, the rest of the Canaanites. God told Joshua that He would drive out all the nations before the children of Israel. Joshua would then divide the inheritance to the nine and one half tribes of Israel and the half tribe of Manasseh.
The moral of this story is that no matter your age, you are still useful to God. Although Joshua was perhaps at least 85 years old at this point, God was still planning to use him to complete the conquest of Canaan. No matter what your age, listen for the voice of God and respond when He says, “Go!”