i was doing a project of making drone parts which i want to 3D print but i don't know how the measurements in blender are going to be the same as the ones in real life so can anyone help me
Most programs see one unit as one milimeter, blender sees it as a meter. This means that the default 2 x 2 x 2 blender cube will appear 2mm x 2mm x 2mm in size when printing. I would personally recommend just remembering that one unit is one milimeter, but if you want the dimensions tab to display the right units you can change it in the properties panel under Scene -> Units by changing the unit preset to milimeters.
Note that setting it to meters or just metric, like the other answer suggests, will only display the size as if it were in meters while it actually still is in milimeters, meaning that you will still end up with a 2 milimeter cube even though blender says it is 2 meters in size.