You didn't say how old so I will assume the source drawings are from V4, V5, or V6. Also not mentioned is imperial or metric units. The native format for TurboCAD is sat. This format will give you the most accurate transfer but the downside is dimensions, annotations, and layer data will be lost. If this data is desired then dwg/dxf is the next best choice.
The dwg/dxf format has changed over the years so the rule of thumb is to use the most current version that both programs support. For example, splines were not supported until R13 and fonts were not supported until R2011.
There has been an on and off bug where dwg/dxf files have been saved as feet even though a metric unit was used. Things to try that have worked in the past are set the units to feet in preferences and then set feet in the Import dialog box if the scale is off by a factor of 12 then close the drawing and re-import as inches. Once the scale is right and if you want to work in metric just re-set preferences to the metric unit of your choice and you should be good to go.