But is it possible to use an DE9 pin to DE 15 pen VGA converter for that?

9 pin monitors are digital TTL, 15 pin are analog. You don't just need an adapter, you also need circuitry to change the signals from digital to analog. Most TTL monitors also had much lower horizontal sync (15kHz vs 31kHz for VGA) so that needs to be converted too.
Some monitors will work with both analog and digital signals, notably old NEC Multisyncs (beware that newer Multisyncs don't work like this; do your research before plugging it in).

This adapter will convert TTL signals to VGA
http://www.ebay.com.au/itm/RGB-CGA-EGA-YUV-VG … #ht_1198wt_1139

However, my advice is that unless you actually have a TTL monitor, just use a VGA video card and monitor, rather than wasting money on that converter trying to use a MDA/CGA/EGA video card with a VGA monitor.

Also, beware that MDA, CGA and EGA are not equal either. Many old EGA//CGA video cards had jumpers to set the output mode. Trying to run a CGA or MDA monitor on a card that outputs EGA may damage the monitor - and vice versa, some EGA monitors will be damaged by MDA input signals.

And is it possible to use an 16-bit ISA VGA card in 8-bit slot for testing purpose only.

Yes, there are many 16-bit VGA cards that will work in an 8-bit slot. Depending on the card, you may need to set a jumper for 8 bit mode.

Is that jumper on the video card? because i have an STB Nitro here.. and having 2 jumper for only 0wait..

Not all video cards will have that jumper. Try it and see. The worst that will happen is the PC just beeps with a video error on POST.

I have tried the XT motherboard. But i think it needs memory first. I will try later when the memory comes in.

http://www.ebay.co.uk/itm/HYUNDAI-HMM-1200-Mo … =item4aae74ae79

pity it's green i suppose, though it has a certain nostalgic value

I looking for a EGA monitor for my XT computer..
And that Monochroom monitor he only sending it to its own country..