how to remove a stand from my iMac

You should reference the year model and not the serial # here in the user to user forum.

To find the exact year model, see > Identify your iMac model - Apple Support

Also FWIW, only the 2006 and 2007 iMac models had a user removable stand. The other models had to be custom ordered from a the factory with a VESA mount.

NathanPerera wrote:

If I give you the model number can you please tell me if I can take off the stand as in the youtube link?

You will need to tell us the exact year model.

To find the exact year model, see > Identify your iMac model - Apple Support

IF the iMac is a 2012 or later the stand is NOT removable, it is integrated into the chassis and simply will not come off. If you are looking for a VESA mount solution try a https://www.bhphotovideo.com/c/product/1338461-REG/tether_tools_vadpt07_rock_solid_vesa_imac_display.html/?ap=y&ap=y&smp=y&smp=y&lsft=BI%3A514&gad_source=1&gbraid=0AAAAAD7yMh1Ys44_iibUpIT9ukYblbkOl