Hi, and welcome.
Can you please provide more context. Are you using WebODM? If so, there are tools to perform measurements:
If not, what platform are you on? Are you familiar with any GIS software, such as QGIS?
If you need more in-depth materials for learning, this book is an incredible resource, and is developed by UAV4Geo, parent organization of OpenDroneMap. Funds contribute directly to improving OpenDroneMap for everyone.