get directory items

I generated presigned urls to upload some images in r2 using the key=

${bookmarkId}/${fileName}

${bookmarkId}/${fileName}

${bookmarkId}/${fileName}

${bookmarkId}/${fileName};
now I want to get the presigned urls of items in the bookmarkId folder, so I use the key=

${bookmarkId}/

${bookmarkId}/

${bookmarkId}/

${bookmarkId}/. But it gives the error: specified key doesnt exist