[Mashiro]

in the picture i can see there is HDMI port but we can convert DVI cable to HDMI port? with any converter is it safe?

Both signals are digital. Only the connector is different. There are already HDMI to DVI cables available and they work. The Raspberry Pi 4 has micro HDMI, so you would need either a) micro HDMI to DVI cable, b) HDMI to DVI with micro HDMI adapter or c) a short micro HDMI to DVI adapter.

Example products:
a) https://www.amazon.com/SIENOC-2x1-8m-Gol...B07D2YSWP8
b) https://www.amazon.com/Cable-Matters-Mic...B00JDRHQ58 (micro HDMI to HDMI adapter) and https://www.amazon.com/AmazonBasics-Inpu...B014I8UQJY (HDMI to DVI cable)
c) https://www.amazon.com/Tripp-Lite-Micro-...00HLDF29I/

If you monitor has HDMI then you simply need a micro HDMI to HDMI cable or adapter with a normal HDMI cable.

You could even get a converter from HDMI to VGA if you only have VGA but I have had bad experience with that because VGA is a old analog signal. So those converters may not work good and may not always work with all devices.