Decode and prefill a question from Q_EED query string

I need to encode values into an url using Q_EED query string, and then prefill questions based on the value of each item.

original values

{'prenom':David,'province':Ontario,'code':y4h3vwer}

final url using q_eed with base64 encoding values

https://qfreeaccountssjc1.az1.qualtrics.com/jfe/form/SV_8dFaixQLtQvpWVE?Q_EED=eydwcmVub20nOkRhdmlkLCdwcm92aW5jZSc6T250YXJpbywnY29kZSc6eTRoM3Z3ZXJ9

I have an Embedded Data Element in my survey’s flow for each of the following parameters :

• prenom
• province
• code

When using basic non encoeded url parameters, I can define each question with a default value using a pipe text form a Embedded Data filed, which looks like this :

${e://Field/prenom}

https://qfreeaccountssjc1.az1.qualtrics.com/jfe/form/SV_8dFaixQLtQvpWVE?prenom=David 

If I want to prefill the decoded “prenom” item from the Q_EED query string, how can I manage this ?