Something like this?

with SampleData as ( -- this cte simply provides the sample data for the query

select

strval

from

(values ('0008.22816'),('069.3142'))dt(strval))

select

strval,

right('0000000' + substring(strval,1,charindex('.',strval) - 1), 7) +

'.' +

right('0000000' + substring(strval,charindex('.',strval) + 1,len(strval) - charindex('.',strval)), 7)

from

SampleData;