Ansible does not have a "df" module to capture the output of the df command. Instead, facts can be used to capture the df output.

Let's say the df command on server1 returns the following.

[john.doe@server1 ~]# df
Filesystem                           1K-blocks     Used Available Use% Mounted on
/dev/sda1                               372607   170989    177862  50% /boot
/dev/sda2                               129774     6994    122780   6% /

Here is how you can get the df output using facts.

---
- hosts: all
  tasks:
  - name: display ansible_mounts
    debug:
      var: ansible_mounts
...

Something like this should be returned. Notice here that size_available and size_total are in bytes, not kilobytes (KB).

• size_available or size_total / 1024 = size in kilobytes (KB)
• size_available or size_total / 1024 / 1024 = size in megabytes (MB)
• size_available or size_total / 1024 / 1024 / 1024 = size in gigabytes (GB)

TASK [display ansible_mounts]
ok: [server1] => {
    "ansible_mounts": [
        {
            "block_available": 9162312, 
            "block_size": 4096, 
            "block_total": 9170560, 
            "block_used": 8248, 
            "device": "/dev/sda1", 
            "fstype": "xfs", 
            "inode_available": 18350077, 
            "inode_total": 18350080, 
            "inode_used": 3, 
            "mount": "/boot", 
            "options": "", 
            "size_available": 182130688, 
            "size_total": 381549568, 
            "uuid": "5629a4fd-3e07-4bfa-a4f7-5b2cccfd6e6e"
        }, 
        {
            "block_available": 9207314, 
            "block_size": 65536, 
            "block_total": 13578240, 
            "block_used": 4370926, 
            "device": "/dev/sda2", 
            "fstype": "xfs", 
            "inode_available": 20597477, 
            "inode_total": 21251126, 
            "inode_used": 653649, 
            "mount": "/", 
            "options": "", 
            "size_available": 125726720, 
            "size_total": 132888576, 
            "uuid": "N/A"
        }
  ]
}

Almost always, there are multiple mounts, which means you'll want to use the loop, with_items or with_list to loop through each item in the ansible_mounts array.

---
- hosts: all
  tasks:
  - name: loop through each ansible mount
    debug:
      msg: "{{ item }}"
    with_items: "{{ ansible_mounts }}"
...