Hi,
save your logs as a string in a variable and use "StringToFile" java action which will convert it to txt file , create a filedocument and name it anything like output.txt and pass it here in java action
You can download the logs from sprintr, or your on-premise-server if you have that. Please explain if you mean another form of logs.
Like the others pointed out, you could (should) use the default log files, or if you create custom log messages anyway, concatenate them in a string variable and create your txt afterwards. If you really have to, you could create a java action to subscribe to a log node at the start of the microflow and then at the end unsubscribe and create your txt.