Dell Inspiron 27 - 7000 HDMI output max resolution of 1920x1080.

According to the tech specs tab on the Dell Sales page, the Inspiron 27 7000 AIO LCD panel is "27-inch FHD* (1920 x 1080)".

*Full High Definition, 1920 x 1080 pixels

So you can't change anything because it's a limitation of the LCD panel.

It's right for the computer LCD that is FHD. However my concern is from the HDMI OUT on the computer that is limited to FHD while my second monitor is UHD (2560x1440). The sale page does not mention the HDMI OUT limitation. The LCD definition is one thing and the HDMI OUT definition capability is an other thing. For example my old Inspiron 2350 have an LCD definition of FHD. but the HDMI OUT have a maximum definition of UHD.

It's totally irrelevant what resolution your Inspiron 2350 supported on its HDMI-Out.

This is in the Service Manual about the HDMI-Out port on the Inspiron 27 7000 AIO:

Video: One HDMI 1.4b port 
NOTE The maximum resolution supported by the HDMI port is 1920 x 1080 at 60 Hz (24-bit).

So FHD is all you can get from the built-in HDMI port with an external monitor on this PC..

A work-around might be a USB3>HDMI dongle that supports higher HDMI resolutions, and is compatible with your version of Windows.

BUT, I don't know if the Intel Iris Xe Graphics in this PC will support any higher resolution on an external monitor when connected via USB3>HDMI.

You'll have to decide if it's worth trying a dongle, hopefully one that you can return if it doesn't do you want...

EDIT: If you're still within the first 30 days of Invoice date, not delivery date, you may be able to return this PC if it doesn't meet your needs. Check Dell's return policy for details and potential shipping and restocking fees.

Re: I cannot understand that Dell builds a high-end computer in 2022 that does not support UHD.

Dell does offer a higher resolution native LCD (UHD) in Inspiron 27 7000 which is a high-end option.  At the same time Dell offers the standard option of FHD.

since you just bought it from Dell, contact them to see if you can upgrade to UHD display.

according to review "The 27-inch Dell Inspiron 7000 is nothing if not customizable...The display screen comes standard with 1080p resolution, and can be upgraded to an optional 4K HDR10 display with spectacular color reproduction."

see spec

@syl.poi  - Assuming you can update to an internal display with higher resolution, does that automatically mean the HDMI-Out port will have higher res too for your external monitor?

I dunno...

So if your resolution is FHD THAT CAN BE UNDERSTOOD AT SIDE OF DELL. MYQUESTION IS THAT WHAT'S RESOLUTION OF YOUR OLD COMPUTER?

Table 1. Display specifications  27-INCH FHD 27-INCH UHD