I would recommend contacting Sig Sauer directly to confirm your P226 uses a #8 sight as some models use #8-8 while others use #8-6. So if you have #8-8 , this set will fit.
We would recommend you get the model specifically for the Sig P238 found here under MPN: TG13SG3PC:
https://www.opticsplanet.com/truglo-brite-site-tfx-pro-day-night-sights-sig-p238-w-6-6-green-tritium-w-or-tg1.html
It will fit the dovetails, this is a #8 front and #8 rear set, which is a reference to the height. It may change your point of aim/point of impact if it that is a different height from your factory sights. The factory front sight should have a #6 or #8 stamped on it as a reference, if you do have a #8 front sight this set will work. If you have a #6 stamped on the front sight you would need the following set:
https://www.opticsplanet.com/truglo-tg13sg2a-tfx-sig-6-front-8-rear-3-dot-green-tritium-fiber-optic-sight.html