You can use the following steps to make the change:
Click on the citation you wish to change.
From Word’s Tools menu, go to the EndNote submenu, and select Edit Citation(s) to display the EndNote Edit Citation dialog. From the EndNote tab, select Edit & Manage Citations.
All of the cited references in the document are listed in the left column of the dialog. An ellipses shows where a citation appears within text. The line below shows the cited references.
Select the appropriate citation from the list at the left of the dialog (you can scroll through all citations in the document) and make any of the following changes to the highlighted citation:
Display as: Author (Year): Select this menu option to display both the author name and the year in the highlighted citation.
Click OK to implement your change(s).
If you do not have the option for Author (Year) you would need to switch your tab in Word:
But it sounds like they are all in the Author (Year) format already, and the Original Poster wants them to be conventional (author, year)? But not sure why they would be already the alternate format.
If that is the case, though, then the unformated citations will look like this {Greaves, 2000 #5209@@author-year} and you can do a simple search and replace to find @@author-year and replace with nothing.
If as an alternative, the OP wants them to be author, year with no parentheses, they will need to edit the citation template to removed the parentheses altogether - but this will apply to everything cited (apart from one specified to use the Author (Year) template.