@Abrar Adil S To use commitment tiers you will have to submit a request through this form and if the request is approved you can update your existing resource pricing tier to a commitment tier or create a new resource with a standard tier pricing plan and then upgrade to the commitment tier. Depending on when you apply for commitment tier you will be charged on pro-rata basis for the first month. If you plan to use the tier for a limited period you can set to do not auto renew and the plan will end on the last day of the month and a standard tier pricing will apply if the plan expires. More details about commitment tier are mentioned here.
Depending on your estimated character count you can estimate the costs of each tier based on the pricing available for each tier.
For document translation you will create the source and target containers on your storage account so they can be used to provide the SAS URI as input documents to the translator endpoint.
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