Snapshot sizes depend on the data written while the snapshot has been the active snapshot. Depending on the VM's write activity, and the snapshot's age, the snapshot files can grow up to the virtual disk's provisioned size (plus some metadata).
To find out what can be done it's necessary that you provide some details like the free disk space on the datastore, and a complete list of files in the VM's folder.
For the file listing, please run ls -lisa *.vmdk in the VM's folder, and post the output as text please (not as a screenshot). For the free disk space you may run df -h.
Do you have other datastores with free disk space (how much)?
André