I think this has been imported from phpBB or other forums, this is not a smile bbCode. The smile bbCode was inserted in source forum and it had been replaced to an image HTML with image source URL. Now you migrated this to wpForo but you forget migrate images from source forum to target server. it search for smileys/bigsmile.gif file, so you should create a /smileys/ folder on WordPress root directory, then upload all smile images of old forum to this folder. In this case it has a chance to work.

For the wpForo just use the simple smile codes:

https://wpforo.com/docs/root/topics-posts/emoticons/

I have a similar problem coming from phpBB where smilies didn't transfer over. In looking at the source code it is looking for:

<img title="fistinair" src="{SMILIES_PATH}/wotf024.gif" alt="wotf024">

Here is the link on the dev site:

https://dev.writersofthefuture.com/forum/the-contest-quarterly-topics-and-other-items/wulf-moons-super-secrets-workshop-challenge/paged/371/

You will see halfway down the page under "Rebel Yell!" a white box that says wotf024, which is the missing smiles.

Trying to figure where to put the folder of the images on the WP side so that they will all relink if possible.

Possibly I might have to do this in the tables using MySQL Workbench, but hoping there is a simpler way to do this.

Thanks. Jason