In your 3D model, there is a beam that has the single part mark "B1".
To find where it is, you can use the Advance Steel search tool ("Search filter" icon on the Advance Steel "Standard" toolbar). Then in the "Search and mark objects" dialog box, you have to:
- Select "Complete model" on the "General" tab.
- Select "Section" (if it is a beam you are searching for) on the "Objects" tab.
- Select "Single part mark" and enter "1" on the "Number" tab.
- Select "Prefix" and enter "B" on the "Number" tab.
Click OK.
The command line shows if such a section has been found in the model.
And the found beam has a red color.
Comment 1: you can have an arrow pointing to the found section by using the "Search marked objects" icon (available on the "Standard" toolbar) so that you can better find it (e.g. in a big model).
Comment 2: to remove the red color of the beam, just click the "Clear marked objects" icon.