Just to clarify, Juicebox-Lite (the free version) has an image limit of 50 images per gallery. Juicebox-Pro has no such image limit.
First of all, it looks like your screenshot is showing a gallery folder (named 'christ2019') rather than the template 'jbcore' folder that the Photoshop plugin uses to create galleries.
After a gallery is created by the plugin, there is no need to modify the gallery folder (no need to rename the Pro 'juicebox.js' file to '~juicebox.js' and place it inside the gallery folder).
As long as the plugin has been updated successfully to Juicebox-Pro, galleries created by the plugin will be Pro without any modification necessary.
Also, in your screenshot, I do not see the 'juicebox.php' and 'pswd.php' files (which are present in the Pro 'jbcore' folder but not in the Lite 'jbcore' folder) so it looks like the gallery folder shown in the screenshot is using Juicebox-Lite.
It looks like you'll need to go through the process of upgrading the plugin from Juicebox-Lite (which the plugin comes bundled with) to Juicebox-Pro.
The procedure is outlined on the plugin's support page here.
Here are detailed instructions.
(1) Unzip the Juicebox-Pro zip file (named 'juicebox_pro_1.5.1.zip').
(2) Navigate inside the extracted 'juicebox_pro_1.5.1/web/' folder.
(3) Copy the entire 'jbcore' folder in this location: 'juicebox_pro_1.5.1/web/jbcore'
(4) Paste the entire 'jbcore' folder inside the 'Presets/Scripts/Juicebox/' folder (in your Photoshop folder).
(5) Navigate inside the 'Presets/Scripts/Juicebox/jbcore/' folder and rename the 'juicebox.js' file to '~juicebox.js'.
Once the plugin has the Pro 'jbcore' folder in place, it can only create Pro galleries.
I also tried installing the standalone JuiceboxBuilder Pro. It also only limits me to 50 images for the gallery.
Please double-check that you are using JuiceboxBuilder-Pro rather than JuiceboxBuilder-Lite.
JuiceboxBuilder-Pro creates only Pro galleries (it cannot create Lite galleries) and JuiceboxBuilder-Lite creates only Lite galleries (it cannot create Pro galleries).
Check your JuiceboxBuilder version (Lite vs Pro) via the 'Help -> About...' option from the drop-down menu at the top.
You can quickly and easily check whether a gallery is Lite or Pro by looking for the Juicebox logo.
All Lite galleries have the Juicebox logo/link in the lower right corner. This branding is not present in any Pro galleries.
I hope my notes above help.
Please let me know how you get on and if I can be of any further assistance.
Just in case your browser is caching and using any Lite files, be sure to completely clear your browser's cache before reloading your gallery's web page.