oka file lo mana name 50times unnappudi aa name ni prathisari bold cheykunda okesari bold cheyalante

You have not mentioned which version of MS Word (such as 2003 / 2007 / 2010 etc) you are using. 
Press Ctrl+F (Ex:pavani) and choose find all. All occurances with pavani will be selected press Ctrl+B to make them bold.