Free storagepool for removing

I have a cluster running 8.1.2 with x200/x410/h500 nodes. I want to get rid of the x200 nodes and need to free that pool x200_36tb_24gb.
I've created a set of filepool policies with rules like

File Matching Pattern: Path == (begins with)
Data Storage Target: h500_60tb_6.4tb-ssd_128gb
Data SSD Strategy: metadata
Snapshot Storage Target: h500_60tb_6.4tb-ssd_128gb
Snapshot SSD Strategy: metadata

for every data dir under /ifs. SmartPool jobs completed several times successfully but there are still 35TB of data in that pool.
How can I identify and move of these files? isi filepool apply -n -v -r couldn't find any data in the x200 diskgroups.