I don't believe there is any way to accomplish this directly even using advanced search. If you're using a numeric field, the advanced operators are: greater than, less than, equal to, etc.  A text field only offers 'equal to' or 'not equal to'. What you want requires a function to evaluate the length of a field, which is not part of search but could be done in workflow. What you might do is use a workflow to perform that calculation and store the result in another field (or otherwise flag it somehow), so you could limit your search by length, such as:

Field: 123456789

Field Length: 9

(You would likely need to allow for the fact that the field could change and thus require the length field to be updated as well.)