how can we change the quotations 3D drawings  downloaded?

Huh?You downloaded a 3D drawing and you want to make a change to it?What drawing did you download?What kind of change do you want to make?We need more details!

Hello Ismail04, by quotations do you mean dimensionning that's to say the measures that you do with the command DIMLINEAR ( COTLIN in french ), DIMALIGNED ( COTALI in french ), DIMANGULAR ( COTANG in french ), etc...
If you want to modificate a dimension in a 3D drawing you will have to set your drawing each time with the UCS ( SCU in french ) of each dimension.
If it's only a light modification you can use the option OBJECT of the UCS, then clic on the dimension, modify it and then do it again for an other.