Is it possible to install ventura on a mac book pro with M3 processor?

The MacBook Pro's with M3 chip began shipping after macOS Sonoma was released so Ventura cannot be installed on a Mac that shipped with Sonoma — unless you are prepared to run Ventura as a guest in the subscription Parallel's Desktop or the free VMware virtual machines.

There is only one free Virtual Machine for an M3 Mac and that is a VMware Fusion (free for personal usage). Although UTM is another free Virtual Machine, it likely will not have the integration and performance of the VMware Fusion software.

I wouldn't recommend a virtual machine solution on an M3 Mac with 8 GB RAM and ideally you would want 32 GB for a Ventura guest operating system. Even 16 GB RAM would be a squeak due to the processing demands of Sonoma and Ventura running concurrently. Be sure to exclude that external drive in your TIme Machine settings and include it in your Spotlight settings : Privacy panel to avoid indexing it.

I suggest purchasing a fast external SSD (e.g. Crucial X8 1 TB or larger) and put the VMware guest operating system on it. This is a USB-C 3.2 Gen 2 rated drive with 1050MB/s and that will enhance the performance of the Ventura guest.

FWIW, it's probably not possible to download Ventura to your M3 MBP in order to create a VM.