You want to know from which paths Terraform is loading providers referenced in your Terraform configuration (files). You need to enable debug messages to find this out.
Which of the following would achieve this?
A . Set the environment variable TF_LOG=TRACE
B. Set verbose logging for each provider in your Terraform configuration
C. Set the environment variable TF_VAR_log=TRACE
D. Set the environment variable TF_LOG_PATH
Although this will only output to stderr and if you need to review log file you will need to include TF_LOG_PATH=pathtofile https://www.terraform.io/internals/debugging