u/Anomaly-XB6783746

Hello guys, kinda new to 3d printing and CAD in general, i got a .3mf mesh file for a part that i wanted, but i wanted to modify dimensions of it of certain sections of that object

i was able to follow tutorials to convert the mesh to a solid, but i am not able to find(and understand) how to change dimensions (see pic below)

my objective is to change the height of the C hook from 21mm to 19mm

and change the height of the blue part from 19mm to 21mm

but i am not able to understand how to do it, i tried making a new part and a new sketch but the changes arent reflected

i also tried creating a pocket and doing changes on there

i'd appreciate a simplified approach for this please