2D ultrasounds are regular standard ultrasounds. You would code depending on the type of ultrasound and the body area being scanned.
Here would be some common ones:
76830 Ultrasound, transvaginal
76831 Saline infusion sonohysterography (SIS), including color flow Doppler, when performed
76856 Ultrasound, pelvic (nonobstetric), real time with image documentation; complete
76857 Ultrasound, pelvic (nonobstetric), real time with image documentation; limited or follow-up
For 3D (billed in addition to the ultrasound), the codes are:
76376 3D rendering with interpretation and reporting of computed tomography, magnetic resonance imaging, ultrasound, or other tomographic modality; not requiring image postprocessing on an independent workstation
76377 3D rendering with interpretation and reporting of computed tomography, magnetic resonance imaging, ultrasound, or other tomographic modality; requiring image postprocessing on an independent workstation
PLEASE NOTE: 3D should not be billed routinely. In my experience, many carriers may bundle or request records. Some may only pay with specific diagnoses. There needs to be medical necessity that the 3D was required to provide additional information not in the 2D scan performed. You may want to review your carrier's policy. Regarding reimbursement, the 2021 CMS allowable is $23.03.
https://www.americanmedicalcoding.com/cpt-code-76376-76377/