Trigger to insert new quote number in this format - database-trigger

Question

I am very new at triggers - actually this will be my first one.
What I am trying to achieve is the following:
When I create a new Sales Opportunity, the Quote no field needs to spit out a number starting from this Q1500/09/2017 so Q is the prefix, 1500 is the first quote number, 09 the month and 2017 the year.
Can someone assist me in getting this right - do i need a SP and a table in order for my trigger to work correctly?
Quote_No is a table field so I'm guessing it should look something like this:
CREATE TABLE [dbo].[Quote_Pref_No](
[Yr] [varchar](4) NULL,
[Mth] [varchar](2) NULL,
[Quote_Pref] [varchar](10) NULL,
[Quote_No] [int] NULL
) ON [PRIMARY]
Then the SP:
Create Proc [dbo].[New_Quote_Num] #ClientID varchar(24),#ContactNum int, #Year varchar(4), #mth varchar(2)
As
Begin
Declare #Pref varchar(5),
#Num int,
#QuoteNo varchar(255)
Select #QuoteNo = B.Description
From dbo.AMGR_User_Fields_Tbl A inner join dbo.AMGR_User_Field_Defs_Tbl B
on A.Type_Id = B.Type_Id and A.Code_Id = B.Code_Id and A.Type_Id = 117
Where A.Client_Id = #ClientId and A.Contact_Number = #ContactNum
Select #Pref = Quote_Pref, #Num = Quote_No + 1
From dbo.Quote_Pref_No
Where Yr = #Year and Mth = #Mth
Set #QuoteNum = 'Q/'+Right(#Year,2)+'/'+Right(#mth,2)+'/'+#Pref+case when Len(#Num) <= 3 then Right('000000'+Convert(Varchar(55),#Num),3) else CONVERT(Varchar(55),#Num) end
Insert into dbo.O_QuoteNo(Client_Id,Contact_Number,Type_Id,Code_Id,O_QuoteNo)
Values(#ClientId,#ContactNum,13,0,#QuoteNum)
Update dbo.Quote_Pref_No
Set Quote_No = #Num
Where Yr = #Year and mth = #mth
End
Grant execute on dbo.New_Quote_Num to CRMGroup
GO
I just dont know how to generate the month and year together.
Trigger code:
Create Trigger [dbo].[QuoteNew]
on [dbo].[AMGR_User_Fields_Tbl] after insert
As
Declare #ClientId varchar(24),
#ContactNum int,
#TypeId int,
#Year varchar(4),
#quoteYear varchar(4),
#mth varchar(2)
Select #ClientId = Client_Id,
#ContactNum = Contact_Number,
#TypeId = TYPE_ID,
#Year = CONVERT(varchar(4),Datepart(yyyy,DateCol)) from inserted
#mth = convert(varchar(2), datepart(mm,Datecol)) from inserted
Select #quoteYear = Yr from dbo.quote_Pref_No where Yr = #Year
select #mth = mth from dbo.quote_Pref_No where mth = #mth
If #TypeID = 117 and #QuoteYear is null or #quoteYear = ''
Begin
Execute dbo.New_Year_Certs #Year
Execute dbo.New_quote_Num #ClientId,#ContactNum,#Year
End
If #TypeID = 117 and #quoteYear = #Year
Begin
Execute dbo.New_Cert_Num #ClientId,#ContactNum,#Year
End
GO
Do I need to create a separate SP for month or can I do both month and year in one SP?