Just use
(.*?)(BUMI.*)$
And then use Regex.Replace:
string outp = Regex.Replace(inp, @"(.*?)(BUMI.*)$", @"${1}<a href="${2}">${2}</a>");
"thanks for you answer, but the BUMI can be other word, maybe some kind of string, like BRMS, or BMRI."
So try this:
string outp = Regex.Replace(inp, @"\$(BUMI.*)$", @"\$<a href="${1}">${1}</a>");