how to get store config value in Magento?

<?php echo Mage::getStoreConfig('isis/isis_order_setting/enable_isis'); ?>

In 2 ways you can find the path of store config value .

1) open Database and see the "core_config_data" table and see the "path" column. find you're module here. and use path value.

2)  open System.xml file and find section, groups and fields values.
you can find this file on app/code/<pool>(community,local,core)/Namespace/Model Name/etc/system.xml
 this is my system.xml file path app/code/local/Magentoo/Isis/etc/system.xml

Below is our dummy system.xml file
<config>
   <sections>
      <isis translate="label">
<groups>
            <isis_order_setting translate="label">
  <fields>
                  <enable_isis translate="label comment">
 </enable_isis>
</fields>
           </isis_order_setting>
         </groups>
     </isis>
  </sections>
</config>