You(and we) can not pronounce"タ三ア". "三" is kanji(Chinese character) means "three". "三" should be "ミ"(katakana). Then you(and we) can pronounce"タミア<tamia>".
Young Buddhist priests took basically a part of the kanji and used it as a phonogram in order to write down quickly lecture of teacher in 9th century. In most, on-yomi<a sound reading=Chinese pronunciation> was used, but there are several katakana that kun-yomi<the Japanese reading=Japanese translation> was used. ミ<mi> is one of them. The letterform of "ミ" has come from "三".
"この 子 が/は タミア。" means "This child is Tamia".