If the interface requires a binary file, yes you can use Base64encoding/decoding. You can check the community commons marketplace module for this. See the following documentation for more information on the type of functions available
https://docs.mendix.com/appstore/modules/community-commons-function-library
and the following link to read how you can call them in a microflow
https://docs.mendix.com/refguide/java-action-call/
Note: in some Mx versions you may see that similar/the same functions are available in the nanoflow commons module.