You can create a new Word Visual Basic (VBA) macro that does what the Find/Replace does by opening your text file in Word and then from the Tools menu > Macros > Macros… panel, select the ScrubCarriageReturns macro name and click Run. That immediately removes all carriage returns in the same manner as the Find/Replace sequence I showed earlier.
To create that Visual Basic Macro, click on the Developer menu item above the ribbon bar. That will show the following ribbon where you click Macros.

That will display this panel where you enter the Macro name exactly as I have entered it.

Click the Edit button, and below the Sub ScrubCarriageReturns() line, enter a blank line and then copy/paste the following VBA code below it.
With ActiveDocument.Range
With .Find
.Text = "^p"
.Replacement.Text = "^p"
.Execute Replace:=wdReplaceAll
End With
End With
End Sub
Now, visit the Word menu and click Save Normal. That saves this VBA macro in your Normal template so you can access it from the Tools menu with this and future documents. Close the Macro Editor window.
Then, for each document that you open that has those CR box symbols in it:
Word > Tools > Macro > Macros and select ScrubCarriageReturns and then click Run. All of the CR boxes will disappear from your open document.