One of the purposes of using PMML or PFA is to provide a translation mechanism which is easy to understand by many applications willing to use models for enhancing its decisioning. Idea is to remove cross technology or cross language barriers. PMML is xml based where as PFA is json based. Thus, one potential solution to your problem could be to build a tool/function which can translate json to xml or vice versa. Doing this would require understanding of both XML and json as well as understanding of data science to identify deviations during translations.
I'm not aware of any tools that convert PFA to PMML. As Karran08 pointed out, both exchange formats essentially solve the same problem, but PFA is more expressive than PMML is. So while I can imagine (not aware of its existence) a tool that converts from PMML to PFA, the other way around would definitely not always be possible.
While PMML has become a widely adopted standard, PFA is still in it's early days it seems and not as widely adopted by producers and consumers. There's also competition from other emerging standards, e.g. ONNX.
Do you have more context to your question? Which tool are you using to generate PFA and does that not support PMML as well?