How to search for newline or linebreak characters in Excel?

In Excel the standard line break Alt + Enter character is ASCII 10. From the look of your screenshot it appears there is another character, probably ASCII 13.

To find these, in the standard Find (or Replace) dialog, in the Find What field, use the standard method of entering ASCII character codes: hold down Alt and type (on the numeric keypad) the character code, i.e., Alt 0010 for just the line break, or Alt 0013 (release Alt and press again) Alt 0010

If that extra character is not a ASCII 13, you can use the function =Code(AString) to get the code of the left most character of a string.

If you press Ctrl + J while in the Find dialog, you will be able to search for those characters.

If you want to do this with a formula, it would be FIND(A3,CHAR(10),...

This is useful if trying to break apart an address block.