Can I connect a iMac 27 2009 mod to Studio Imac 2022 with target display mode

The 2022 Mac does not support Target Display Mode.

carefully read > Use your iMac as a display with target display mode - Apple Support

• The other Mac that you're connecting it to must have been introduced in 2019 or earlier and have macOS Catalina or earlier installed.

The shop where i bought the iMac studio said that this was ok...

Blame the internet. When the work-from-home movement arose with the onset of COVID, there was a mad rush by online "reporters" to talk up using an iMac as a monitor. Lacking both editorial support and, apparently, the most basic research skills, they made it sound like any iMac could be a monitor for every other tech device in existence.

The old saying, " if people see lies enough, they become the new truth," is fully at play here.

Even some Apple employees, who could quickly check the support Target Display Mode article for sysreqs, were instead telling people what the post-process horse feed on the internet said. Sad.

Yes, there was a quirk in SOME 2009/2010 27-inch iMacs them let then work as monitors for devices other than Mac computers. It was never a sure thing. And here the real rub: Even were your 2009 and a Studio capable, the required Thunderbolt cabling and adapters the Studio needs can cost almost as much as a really decent external monitor new!

No.

See: Use your iMac as a display with target display mode - Apple Support

I said first. 😎

Well not according to Apple or the Support article.