In order to have correct lengths you need to define and convert units correctly. In any computer software package lengths are measured using floating point numbers that do not have any meaning on their own like for example 15.758, or 3, or 250.5. In one way or another a unit like a meter, a nanometer, a foot, a lightyear or anything else needs to be assigned to the numbers so for example 1 becomes 1 meter, 2 becomes 2 meters and so on. In different programs or even different contexts using the same software different units are used. They need to be converted correctly.
First of all you need to know what units are used in the files you have. Then you also need to choose what units you want to use in Blender:
When you know these two things - the units in your files and the units you are using in Blender - you will know if you need any conversion when importing.
For example: the interior designers I work with are used to working in millimeters, however I work in meters in Blender. I ask them to export the drawings in meters to DXF and they do so. I do not need to adjust anything and get the scale correctly when importing.
If they exported the drawings in millimeters I would need to set the unit scale to 0.001 when importing because a millimeter is 0.001 of a meter.
Same goes for feet - I would set the unit scale to 0.3048 if I chose to work in meters.
You could also scale the units. If it's feet that need to be converted to meters you would select the imported curves and hit s followed by 0.3048.