The tub/shower unit seems to be made of acrylic, has no lines and looks like it is only one piece. I would like to replace it with a newer version with higher walls. Is this possible and if so how?

the Tub-to-Shower Conversion Kits can be customized to fit nearly all shower enclosure sizes and conditions much more quickly and affordably than rigid one-piece acrylic or composite-shower pans.

Bath Fitter creates a bespoke piece of acrylic (or whatever ... Bath Fitter can install your new bathtub or shower enclosure and walls in as little as one day. One reviewer, Ingolf in New York ...