how do i subsequent dimensioning and scaling a Drawing from DXF-File

Hello,
i'm a newbie in CAD and LibreCAD.
Therefore my question is quite simple.
I want scale a dxf File of the attached picture to 50cm.
Unfortunately i cannot find any dimension or scale tools for an existing imported file.
After i imported the dxf, it is very small.
How could i bring the object to the dimension 50 cm height and width?

Regards
Jens

Measure the imported picture with the info tool distance point to point from edge to edge.
Call up Tools - Modify - Scale:

At x insert 50/measured value, if the measured value is smaller than the wanted (50), or if bigger the other way around. Maths is a weak spot of mine.