Reading the codeZX38 means a ZX cogged belt with a 38 inch inside length (965mm). Metric sizes may show the inside length (Li) or the datum length (Ld), which is 22mm longer, so check which your belt uses.
Upgrading from Z?A ZX belt runs in the same pulleys as a smooth Z belt of the same length, so a ZX38 can usually replace a Z38 directly. Every belt here fits standard Z section pulleys.
ZX or XPZ?A ZX belt is 10mm wide and 6mm deep. An XPZ cogged wedge belt looks similar but is deeper, at 8mm, and runs in SPZ pulleys, so measure the depth to be sure.