Hi Tim, you have a second generation Millenium Pro, which does not have a typical dovetail.
Here is an optics plate designed for the Gen 2 >>>
https://opticsfactory.com/red-dot-sight-for-taurus-g2-g3-tx22/TaurusG2Plate
Or you could find a gun shop that does slide milling and have the slide milled for the footprint of your choice.
Stay safe & have a great day!

You will need to remove the rear sight and install an optic mounting plate. Otherwise, you’d have to hire a gunsmith to mill the receiver. 🔫

Good morning to you!! Your only option is to remove the rear sight and install an optic mounting plate. Doing so will keep you from having to get a gunsmith to mill the receiver. Hope this helps. Have a good rest of your day.
🇺🇸🇺🇸 'Merica' 🇺🇸🇺🇸

Hi Tim and welcome. The needed optics plate is here: https://opticsfactory.com/red-dot-sight-for-taurus-g2-g3-tx22/TaurusG2Plate ------ I also highly recommend the OSight SE with the RMSc/Holosun K footprint: budsgunshop.com/product_info.php/products_id/183167/olight+osightse+2moa+dot+32moa+circle+red+dot ---------- Cheers, stay safe and enjoy!

Yes, you can mount an optic on a Taurus Millennium Pro PT-140 by using a dovetail adapter plate that replaces the rear sight. These mounts enable the use of popular micro red dots (e.g., Vortex Venom, Burris FastFire) without custom slide milling, fitting models like the PT-140 G2.
Key Mounting Information:
Mounting Method: Specialized adapter plates replace the factory rear sight.
Compatibility: Look for plates designed for the "Taurus G2C/G2S/PT111/PT140/G2/PT709/PT740" series.
Optic Footprints: Supported footprints often include Doctor/Vortex Venom/Burris FastFire.