You need two modules, a booster module, because you have to go up to 12v higher than 7.2v and a step-down module, because the output needs to be 5V. 6V. The module is not expensive, I have both kinds of modules, bought on Taobao, it is very useful.
Simple connection: Input terminal: 7.2v, output terminal is connected to electrical equipment. (Note to distinguish the positive and negative poles) are dc to dc modules.