You can use the Java keytool to convert *.pfx to *.jks.
It is included in the Java JRE
https://www.oracle.com/technetwork/java/javase/downloads/jre8-downloads-2133155.html
Change to the \bin directory and run keytool
cd "C:\Program Files (x86)\Java\jreX.X.X_xxx\bin"
keytool -importkeystore -srckeystore certificate.pfx -srcstoretype pkcs12 -srcstorepass PASSWORD -srcalias Source_Alias -destkeystore output.jks -deststoretype jks -deststorepass PASSWORD -destalias ALIAS
Get alias from current *.pfx
keytool -v -list -storetype pkcs12 -keystore certificate.pfx > output.txt
Open output.txt and look for the line starting with “Aliasname:”