Have a look at wp_get_attachment_image_url
for getting the URL of images: https://developer.wordpress.org/reference/functions/wp_get_attachment_image_url/
or wp_get_attachment_url
for getting the URL for attachments other than images: https://developer.wordpress.org/reference/functions/wp_get_attachment_url/.
These functions return the URLs only and you could use them like so:
// your JSON
$json = '
{
"Gallery Images": [
"1833",
"1834",
"1835"
]
}
';
// convert it to PHP array
$array = get_object_vars( json_decode( $json ) );
// loop through array and get the image URLs
foreach ( $array['Gallery Images'] as $id ) {
$image_url = wp_get_attachment_image_url( $id );
}
You could also retrieve more than just the URL, wp_get_attachment_image_src
for example returns width and height of the image file as well: https://developer.wordpress.org/reference/functions/wp_get_attachment_image_src/.