Error: gradlew: The term 'gradlew' is not recognized as the name of a cmdlet, function, script file, or operable program.(Apache ofbiz)

Question

I have a subject at school where I have to install the Apache Ofbiz ERP software. I have downloaded Ofbiz version 18.12.06 and Java 8. Then I followed the instructions in the 'README' file. But when I run the command gradlew cleanAll loadAll, I get an error message

gradlew : The term 'gradlew' is not recognized as the name of a cmdlet, function, script file, or operable program. Check the 
spelling of the name, or if a path was included, verify that the path is correct and try again.
At line:1 char:1
+ gradlew cleanAll loadAll
+ ~~~~~~~
    + CategoryInfo          : ObjectNotFound: (gradlew:String) [], CommandNotFoundException
    + FullyQualifiedErrorId : CommandNotFoundException

Then I installed Gradle-4.9 and ran the 'gradle cleanAll loadAll' command, but I still get an error.

gradle : 
At line:1 char:1
+ gradle cleanAll loadAll
+ ~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (:String) [], RemoteException
    + FullyQualifiedErrorId : NativeCommandError
 
FAILURE: Build failed with an exception.
* Where:
Build file 'C:\Users\HP\Downloads\apache-ofbiz-18.12.06\apache-ofbiz-18.12.06\build.gradle' line: 60
* What went wrong:
A problem occurred evaluating root project 'ofbiz'.
> Could not find method java() for arguments [build_4rt6fvg59269rv3cik9godb792$_run_closure1@f6900a] on root project 'ofbiz'.
* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.

I really hope to receive help from everyone.

I then tried installing different versions of Gradle, but the issue persists. I also tried installing Ant-Apache as instructed in some online resources, but it didn't solve the problem.