๑۩۞۩๑ <<<< is there many of this kind of codes? that can't be seen naturally on mirc?

It all depends on the font type your using and if its your font folder.

i mean //echo -a it

It shows fine on mine it shows like 2 arrows that are up with a circle in the middle

yeah hehehe that one is there any other codes like that?

Well they're not special "codes". What you've pasted is UTF-8 encoded text, which means that as long as users have a UTF-8 capable IRC client (which mIRC is, provided the "UTF-8 display" option is turned on), they will see that text as five Unicode characters:

U+0e51 (Thai digit one)
U+06e9 (Arabic Place of Sajdah)
U+06de (Arabic Start of Rub El Hizb)
U+06e9 (Arabic Place of Sajdah)
U+0e51 (Thai digit one)

Of course on non-UTF-8 capable IRC clients they appear as a mess of ASCII (or whatever the client's supported encoding is) characters.

The important thing to realise is that there's nothing magical or special about those characters, they're just UTF-8 encoded text, which supports characters, symbols, and other glyphs for thousands of different languages.

how can i or anybody do something like that or is there any like that code on mirc?

The simplest way is to open up the Windows Character Map (you can type /run charmap from mIRC).

Character Map will only list the glyphs (characters) available for the selected font, so make sure you select something like Arial or Times New Roman which have a wide range of characters available. You should then be able to see a list of all available characters for that font, and you can select the ones you want to copy to the clipboard and paste them into mIRC.

Before you try pasting into mIRC, open up the font dialog for the window you want to paste into (type /font) and make sure the UTF-8 dropdown is set to Display and encode. If it isn't then the text will be garbled when you send the text