You can use Movable Type's search and replace functionality either to search through all of your entries for a particular string, or to replace all instances of a string with another string. IMPORTANT: there is no undo feature, so be careful when you use the replace functionality; because of this you may want to export your Movable Type entries before using replace, for backup purposes.
You have the following options when using search and replace:
Case Sensitive box. This means that the string foo will match
foo, Foo, fOo, etc.
Regular Expression Match. If you are unsure what this means, you
would do best to leave this box unchecked.
Title, Entry Body, and
Extended Entry Body fields of each entry in your weblog. You can tune the
search and replace to operate on only a subset of these fields by checking and
unchecking the Search fields boxes.