If you neither use EAGLE nor have an STL file of your PCB, you can convert other data output formats (e.g. STEP) of your PCB with online offers such as '3D Transform' into an STL file or use a program such as FreeCAD to convert from IDF to STL.
Please note that the order of the 3D model must be done before the order of the matching PCB.
If you order the circuit board that fits the 3D-Model in the PCB-POOL within 14 days of delivery, your 3D-order will go to FREE-FITS-or-NOT, i.e. you will receive your 3D-Model at no charge.
Please be patient while your file is transferred.