If you redefine the style all the drawings are using to match the style you're after, you can save the updated style to your master library.
Then on each sheet you could update it.
Another way would simply be to go to each sheet and right click to choose select all Inventor dimensions and switch to the newer style.
The first requires you open each idw file. The second requires you open each idw AND go to each sheet in it.
To do it globably with a single command you're looking at a VBA macro\add-in that will do a bunch of idw's at once. Should be pretty straight forward, pick a folder, open each file, swap dim styles, save, close, repeat. I've written macros that pull all the files in a folder and change a bunch of user parameters. Should be close to the same thing.
Welcome to the forum.
You might also want to take what has been suggested and incoporate that into an iLogic routine. Then by just running the rule it would do this automatically.
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