The simplest way, assuming your O.S. setup is Raspbian based (is it?) is to use the provided "SD Card Copier" ** software (AKA piclone, rpiclone) and a USB-based uSDHC card reader/writer.
** Should be found in the "Accessories" sub-menu as per this, albeit an old "Jessie", screenshot:
http://www.cpmspectrepi.uk/raspberry_pi ... Screenshot
and, FWIW, a few screenshots of (that early version of) the tool in use: http://www.cpmspectrepi.uk/raspberry_pi ... _a_Pi_Zero
Still running Raspbian Jessie or Stretch on some older Pi's (an A, B1, 2xB2, B+, P2B, 3xP0, P0W, 2xP3A+, P3B+, P3B, B+, and a A+) but Buster on the P4B's. See: https://www.cpmspectrepi.uk/raspberry_pi/raspiidx.htm