yes it will fit just fine

Hi Matthew and welcome. Yes, it will fit the Springfield XDM 3.8 no issue.
Fits:
Large Semi Auto Pistols:
Beretta 92, 96
Glock 17, 19, 21, 22, 23, 26, 27, 29
Glock 30, 31, 32, 33, 34, 36
H&K P2000
H&K USP 40
H&K USP 45
H&K USP 9
H&K USP compact 40
H&K USP compact 45
H&K USP compact 9
High Point 380
High Point 9mm
Ruger P85, P89, P90, P93, P94, P95
S&W 3904, 3914, 3953, 3954
S&W 4003, 4004, 4006
S&W 4013, 4014, 4043
S&W 4044, 4046, 4054
S&W 4506, 4526, 4546
S&W 5903, 5906, 5924
S&W 5926, 5943, 5944
S&W 99
S&W M&P 40, M&P 45, M&P 9
Springfield XD 3"
Springfield XD 4"
Springfield XD 5"
Springfield XD M
Taurus 945
Taurus PT100, PT101, PT111, PT140, PT145, PT9
Walther P99
Cheers and stay safe!

As well as it will.