You have an old EMB design file that was digitized for a specific fabric without Auto Fabric. Now you want to use this design for a production on a very different fabric. Applying Auto Fabric with that new fabric on this design file is what you need. The software will re-calculate the Pull Compensation and the Underlay according to the new Fabric.
Please follow the procedure outlined below:
1) Go to File > New from Template… menu
2) In the New from Template dialog box, make sure the checkbox of Auto Fabric is checked
3) Click on the OK button
Note: a new design is started with Auto Fabric applied.
4) Go to File > Import Embroidery… menu
5) In the Import Embroidery dialog box, select the emb file
6) Click on the Open button
Note: the design is opened with Auto Fabric ON
7) Go to Design > Auto Fabric… menu
8) In the Auto Fabric dialog box, select a fabric in the fabric list
9) Click on the OK button to apply
Note: at the point, a fabric has been applied to the design.